There are numerous requirements for the accurate measurement of fluid flow through pipelines. This is particularly true in the measurement of natural gas and liquid petroleum products where the value of the products passing through the pipeline is very great. Particular applications for fluid measurement in pipelines include:
1. Throughput measurement for custody transfer. PA0 2. Peak loading control systems. PA0 3. Blending systems. PA0 4. Pacing of gas samplers. PA0 5. Pacing of gas odorizers. PA0 6. Compressor surge control.
Fluid flow in pipelines is most typically measured by the use of orifice plates. However, there is an increasing use of turbines for pipeline flow measurement. This includes both full flow turbines and insertion turbine meters.
Any type of flow measurement system for pipelines requires periodic calibration to insure that the fluid measurement is accurate. The equipment required for an orifice metering system and its calibration typically include a complete bypass pipeline segment and additional hardware including upstream and downstream block valves, a pass line, orifice flanges, upstream and downstream flanges, as well as additional orifice plates, transducers and various parameter recorders. The calibration system typically requires at least a temporary shut-down of the pipeline. The calibration equipment and related hardware also constitute a substantial capital expense.
One method which has been proposed for the calibration of fluid flow through pipelines is the use of multiple flow lines in a main pipeline with each flow line having a line meter. One flow line is provided with a calibrated master meter. A piping and valve arrangement is provided in which the flow through any one of the line meters can be directed through the master meter such that each of the line meters can be calibrated. Such a system, however, utilizes an expensive combination of multiple lines, multiple line filters, valves and valve operators which in turn require extensive operator control and maintenance.
In view of the importance of calibrating fluid flow in pipelines and the expense heretofore incurred for such calibration, there exists the need for a method and apparatus for rapidly, accurately and inexpensively proving the metering of fluid through pipelines without the necessity for shutting down the pipeline or building an extensive network of pipeline bypasses and related equipment.